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An Analytical Isotherm Equation (CONICA) for nonideal mono- and bidentate competitive ion adsorption to heterogeneous surfaces

van Riemsdijk, Willem H.; de Wit, Johannes C.M.; Mous, Sipko L.J.; Koopal, Luuk K.; Kinniburgh, David G.. 1996 An Analytical Isotherm Equation (CONICA) for nonideal mono- and bidentate competitive ion adsorption to heterogeneous surfaces. Journal of Colloid and Interface Science, 183 (1). 35-50. 10.1006/jcis.1996.0516

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Abstract/Summary

Analytical isotherm equations for the competitive binding of protons and other cations to heterogeneous surfaces have been derived. These extend our earlier nonideal competitive adsorption (NICA) equation by considering bidentate as well as monodentate binding of ions. The protonation of these bidentate sites occurs in two COnsecutive steps. The CONICA model equations separate the apparent heterogeneity into a generic heterogeneity characteristic of all of the surface sites and an ion-specific contribution characteristic of each type of ion. The CONICA model was combined with a simple Donnan model to account for electrostatic effects and was fitted both to proton binding at various ionic strengths and to the pH-dependent binding of Cu (pH 4, 6, and 8) to a purified peat humic acid. Model fits were good. The measured H+/Cu2+exchange ratio is significantly greater than one for the whole pH range, which indicates the importance of the bidentate binding mechanism for copper.

Item Type: Publication - Article
Digital Object Identifier (DOI): 10.1006/jcis.1996.0516
Programmes: BGS Programmes > Groundwater Management
Additional Keywords: GroundwaterBGS, Groundwater
Related URLs:
Date made live: 02 Dec 2010 15:00
URI: http://nora.nerc.ac.uk/id/eprint/12468

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